System
Figure 8-1, Object design closes the gap between
application objects identified during requirements
and off-the-shelf components selected during
Problem
system design.
Application objects
Requirements gap
Solution objects
Custom objects
Object design gap
Off-the-shelf components
System design gap
Bernd Bruegge & Allen H. Dutoit
Object-Oriented Software Engineering: Using UML, Patterns, and Java
Machine
1
Figure 8-2, Activities of object design (continued on
next slide).
Select Subsystem
Specification
Identifying missing
attributes & operations
Reuse
Identifying components
Specifying visibility
Adjusting components
Specifying types &
signatures
Identifying patterns
Specifying constraints
Specifying exceptions
Bernd Bruegge & Allen Dutoit
Adjusting patterns
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
2
Figure 8-2, Continued.
Check Use Cases
Restructuring
Optimization
Revisiting
inheritance
Optimizing access
paths
Collapsing classes
Caching complex
computations
Realizing associations
Delaying complex
computations
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
3
Figure 8-3, An example of implementation
inheritance (continued on next slide).
Object design model before transformation
Object design model after transformation
Hashtable
Hashtable
put(key,element)
get(key):Object
containsKey(key):boolean
containsValue(element):boolean
put(key,element)
get(key):Object
containsKey(key):boolean
containsValue(element):boolean
table 1
1
MySet
MySet
put(element)
containsValue(element):boolean
put(element)
containsValue(element):boolean
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
4
Figure 8-3, continued.
/* Implementation of MySet using
inheritance */
class MySet extends Hashtable {
/* Constructor omitted */
MySet() {
}
void put(Object element) {
if (!containsKey(element)){
put(element, this);
}
}
boolean containsValue(Object
element){
return containsKey(element);
}
/* Other methods omitted */
}
Bernd Bruegge & Allen Dutoit
/* Implementation of MySet using
delegation */
class MySet {
private Hashtable table;
MySet() {
table = Hashtable();
}
void put(Object element) {
if (!containsValue(element)){
table.put(element,this);
}
}
boolean containsValue(Object
element) {
return
(table.containsKey(element));
}
/* Other methods omitted */
}
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
5
Figure 8-4, Inheritance meta-model.
Inheritance
Inheritance detected
during specialization
Bernd Bruegge & Allen Dutoit
Taxonomy
Inheritance
for Reuse
Inheritance detected
during generalization
Specification
Inheritance
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
Implementation
Inheritance
6
Figure 8-5, An example of design pattern: Adapter.
Client
ClientInterface
LegacyClass
Request()
ExistingRequest()
adaptee
Adapter
Request()
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
7
Figure 8-6, Applying the Adapter design pattern to the
Set problem of Figure 8-3.
Client
Set
Hashtable
add(element)
put(key,element)
adaptee
MySet
add(element)
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
8
Figure 8-7, Applying the Bridge design pattern for
abstracting database vendors.
Arena
LeagueStore
Stub Store
Implementor
Bernd Bruegge & Allen Dutoit
imp
LeagueStoreImplementor
XML Store
Implementor
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
JDBC Store
Implementor
9
Figure 8-8, Applying the Adapter design pattern for
sorting Strings in an Array. See source code in Figure
8-9.
Array
Comparator
MyString
compare()
greaterThan()
equals()
adaptee
MyStringComparator
compare()
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
10
Figure 8-9, Adapter design pattern example.
/* Existing target interface */
interface Comparator {
int compare(Object o1, Object
o2);
/* ... */
}
/* Existing client */
class Array {
static void sort(Object [] a,
Comparator c);
/* ... */
}
/* Existing adaptee class */
class MyString extends String {
boolean equals(Object o);
boolean greaterThan
(MyString s);
/* ... */
}
Bernd Bruegge & Allen Dutoit
/* New adapter class */
class MyStringComparator implements
Comparator {
/* ... */
int compare(Object o1, Object o2) {
int result;
if (o1.greaterThan(o2)) {
result = 1
} else if (o1.equals(o2)) {
result = 0;
} else {
result = -1;
}
return result;
}
}
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
11
Figure 8-10, Applying the Strategy pattern for
encapsulating multiple implementations of a
NetworkInterface.
Application
NetworkConnection
LocationManager
open()
close()
send()
receive()
send()
receive()
setNetworkInterface()
Ethernet
open()
close()
send()
receive()
Bernd Bruegge & Allen Dutoit
NetworkInterface
WaveLAN
open()
close()
send()
receive()
UMTS
open()
close()
send()
receive()
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
12
Figure 8-12, Applying the Abstract Factory design
pattern to different intelligent house platforms
TheftApplication
HouseFactory
createBulb()
createBlind()
EIBFactory
createBulb()
createBlind()
LuxmateFactory
createBulb()
createBlind()
LightBulb
EIBBulb
Bernd Bruegge & Allen Dutoit
LuxmateBulb
Blind
EIBBulb
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
LuxmateBulb
13
Figure 8-13, Applying the Command design pattern to
Matches in ARENA.
Match
*
play()
replay()
Move
execute()
«binds»
GameBoard
TicTacToeMove
execute()
ChessMove
execute()
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
14
Figure 8-14, Anatomy of a preference dialog.
Aggregates, called Panels, are used for grouping user
interface objects that need to be resized and moved
together.
Top panel
Main panel
Button panel
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
15
Figure 8-15, UML object diagram for the user
interface objects of Figure 8-14.
prefs:Window
top:Panel
title:Label
main:Panel
c1:Checkbox
buttons:Panel
ok:Button
c2:Checkbox
cancel:Button
c3:Checkbox
c4:Checkbox
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
16
Figure 8-16, Applying the Composite design pattern to
user interface widgets.
Component
*
move()
resize()
Label
Button
Checkbox
Composite
move()
resize()
Window
Panel
Applet
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
17
Figure 8-17, An example of dynamic site with
WebObjects.
WebBrowser
WebServer
StaticHTML
WebObjectsApplication
WOAdaptor
WoRequest
WORequest
Template
EOF
RelationalDatabase
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
18
Figure 8-18, WebObject’s State Management Classes.
The HTTP protocol is inherently stateless.
WOAdaptor
WORequest
WebServer
WOSessionStore
*
WOApplication
*
WOSession
Bernd Bruegge & Allen Dutoit
*
WOComponent
* DynamicElement
*
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
19
Figure 8-19, ARENA analysis objects related to Game
independence.
Arena
LeagueOwner
Statistics
League
Game
Tournament
Player
Move
TicTacToe
Match
Chess
Result
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
20
Figure 8-20, Applying the Abstract Factory pattern to
Games
Tournament
Game
createMatch()
createStatistics()
TicTacToe
createBulb()
createBlind()
Match
TTTMatch
Bernd Bruegge & Allen Dutoit
Chess
createBulb()
createBlind()
Statistics
ChessMatch
TTTStats
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
ChessStats
21
Figure 8-21, Applying the Command design pattern to
Matches and ReplayedMatches in ARENA.
Match
ReplayedMatch
nextMove()
previousMove()
*
play()
replay()
«binds»
GameBoard
Move
execute()
TicTacToeMove
ChessMove
Bernd Bruegge & Allen Dutoit
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
22
Figure 8-22, Applying the Observer design pattern to
maintain consistency across MatchViews.
observers
Subject
1
subscribe(Subscriber)
unsubscribe(Subscriber)
notify()
GameBoard
state
getState()
playMove()
Bernd Bruegge & Allen Dutoit
Observer
*
update()
MatchView
gameBoard
update()
Object-Oriented Software Engineering: Conquering Complex and Changing Systems
23